1. Field of the Invention
The present invention relates to an image forming apparatus to obtain a color image by superposing plural colored images in an electro-photographic copier or printer.
2. Description of the Related Art
In such image forming apparatus as copiers/printers, a tandem type image forming apparatus to obtain a color image by transferring multiple toner images formed on the plural number of photosensitive drums arranged in parallel is known. In such the tandem type image forming apparatus as this, the apparatus is demanded to be small in size despite of plural number of photosensitive drums arranged in recent years. In the Japanese Patent Application Publication No. 2001-125337, an image forming apparatus with the plural number of image forming units arranged in a row below an intermediate transfer belt is disclosed. This conventional image forming apparatus is in a structure that the image forming units are arranged below an intermediate transfer medium and two-component developing units are arranged under photosensitive drums. Thus, in the conventional image forming apparatus, stabilized amounts of developers are supplied, a space for developing units is saved and the image forming apparatus is downsized.
However, in this conventional tandem type image forming apparatus, an exposing device to expose a photosensitive drum of image forming unit is arranged below the developing unit. Furthermore, because of the developing rollers of the developing units are positioned close to the exposing positions, toners scattered from the upper developing rollers fall and accumulate on the upper surface of the exposing device. That is, a laser projection window of the laser beam exposure device is stained and the laser is intercepted by dropping matters such as scattered toners, etc. and image quality can be deteriorated.
Therefore, a tandem type image forming apparatus capable of preventing the stain of the laser projection window of an exposing device arranged below developing units by scattering toners and forming good and stable electrostatic latent images irrespective of plural image forming units arranged along the lower side of an intermediate transferring belt is so far demanded.